1. Field of the Invention
The present invention relates to an electrostatic chuck device and more specifically, to an electrostatic chuck device which is suitably used when adsorbing and fixing a plate-shaped sample such as a semiconductor wafer or a glass substrate for a liquid crystal device by an electrostatic force and in which even in various processes such as film formation treatment by a physical vapor deposition method (PVD) or a chemical vapor deposition method (CVD), etching treatment such as plasma etching, and exposure treatment in a semiconductor manufacturing process, wear resistance is high and it is possible to control the plate-shaped sample to have a desired temperature.
Priority is claimed on Japanese Patent Application No. 2013-115394, filed May 31, 2013, the content of which is incorporated herein by reference.
2. Description of Related Art
In the past, in a manufacturing process of a semiconductor device, a liquid crystal device, or the like, applying various treatments to the surface of a plate-shaped sample such as a semiconductor wafer, a metal wafer, or a glass substrate has been performed, and at the time of various treatments, an electrostatic chuck device has been used in order to fix the plate-shaped sample by an electrostatic adsorption force and maintain the plate-shaped sample at a preferable constant temperature.
The electrostatic chuck device has, as an essential component, an electrostatic chuck section with an internal electrode for electrostatic adsorption provided in the inside or the lower surface of a ceramic plate-shaped body that is a dielectric body, and the plate-shaped sample such as a semiconductor wafer, a metal wafer, or a glass substrate is placed on the surface (adsorption surface) of the ceramic plate-shaped body and is adsorbed and fixed onto the adsorption surface of the ceramic plate-shaped body by an electrostatic adsorption force which is generated by applying a voltage between the plate-shaped sample and the internal electrode for electrostatic adsorption.
In such an electrostatic chuck device, there is a device to cool the plate-shaped sample by making inert gas such as helium gas flow between the adsorption surface of a ceramic plate-shaped body and the plate-shaped sample for the purpose of controlling the temperature of the plate-shaped sample being processed or being treated, and various improvements for improving various characteristics such as the sealing characteristics of the inert gas or the detachment characteristics of the plate-shaped sample such as a wafer have been performed.
For example, an electrostatic chuck is proposed in which variation in the temperature of a substrate to be treated, which is caused by contact unevenness in a seal ring, does not occur due to providing the seal ring at a peripheral border portion of a placement surface on which the substrate to be treated is placed, of a base material, providing a plurality of projection portions having the same height as the height of the seal ring, in an area surrounded by the seal ring of the placement surface, and determining an arrangement pitch of a plurality of projections and a positional relationship between the projection closest to the seal ring and the seal ring (Japanese Unexamined Patent Application, First Publication No. 2009-111243).
Further, an electrostatic chuck is proposed in which the detachment characteristics of a wafer or the amount of leakage of gas is improved by providing an annular convex portion at an outer peripheral end portion of a placement surface on which the wafer is placed, of a base material, providing an annular concave portion inside the annular convex portion, providing a smooth concave surface inside the annular concave portion, and defining a positional relationship between the annular convex portion and the annular concave portion and average roughness Ra of a contact surface with a plate-shaped sample, for example, making a contact surface of the annular convex portion protrude higher than the concave surface, or the like (Japanese Patent No. 4942364).
Further, in order to make heat conduction of a plate-shaped sample uniform, it is necessary to reduce a contact area between the plate-shaped sample and a base material on which the plate-shaped sample is placed, and therefore, reducing the contact area by forming projections on a placement surface of the base material is performed.
As electrostatic chucks, an electrostatic chuck of a type in which the electrical resistivity of a dielectric layer is set to be in a range of 1×108 Ω·cm to 1×1012 Ω·cm, thereby performing adsorption by a Johnsen-Rahbek force, and an electrostatic chuck of a type in which the electrical resistivity of a dielectric layer is set to be greater than or equal to 1×1014 Ω·cm, thereby performing adsorption by a Coulomb's force are known.
Incidentally, in a case where a contact area with a wafer is reduced in a Johnsen-Rahbek force type electrostatic chuck, an electric current is concentrated on a contact portion, and therefore, a problem such as heat generation or non-uniformity of plasma occurs.
Therefore, an electrostatic chuck device is proposed in which a contact area with a wafer is reduced by using an aluminum oxide-silicon carbide composite sintered body that is a dielectric body having a high adsorption force in a Coulomb's force, for a material of a base material on which a plate-shaped sample is placed, and providing minute projection portions on an electrostatic adsorption surface of the base material (Japanese Patent No. 4739039).
Further, an electrostatic chuck device is proposed in which flip-up of a wafer or the uniformity of temperature is improved by providing concentric annular projections at an outer peripheral border portion of a placement surface of a base material, on which a plate-shaped sample is placed, and inside thereof, and making the height of the inner annular projection higher than the height of the outer annular projection (Japanese Patent No. 4909424).